Alloy articles for high-temperature service



Patented July '4, 1950 g,g', 3,4,'71 vv ALLOY ARTICLES FOR HIGILTEMPERAQ TURESERVICE'f Russell Franks. and; William Binder; Niagaraa, Eal ls,..N. X. assignors, by:mrsnesas s.i mmmts; c

to Union. Carbide and Carbon: Corpgratiom No Drawingl 'Application-'May' 9fl9e6i H m; SerialNo. 668 333 This ,invention relates, to jer'rous use at high, temperaturea rc aferrin'g ;more particularly to alloys suitable for use in applications where greatstrength at high temperatures is required. '7 v The trend oimodern engineering istoward the utilization of hightemperatures for many and diverse operations.. F0 3;; eXample,-., chemical processes-are today cQnductedat. very high tem- I peratures-,,a, notable instance .being petroleum refining. Also,, the quest for. improved power sourceshas -led to the investigation and. development. of; such devices as; superchargers, gas turbinea.jet,propuisionyapparatus and the like all operating 'at high temperatures. These developments.=demand of the metallurgist v metals and alloys which will withstand prolonged exposure to temperatures well-above about 700 F. and in many instances well above about 1ZO0 R; The problemis complicated therfact that severe mechanical stress is often encountered at these temperatures.- I 7 For parts of such devicesas superchargers, gas turbines, jet propulsion apparatus and the like, it is necessary to employ alloys that are capable of withstanding severe mechanical. stress at high temperatures. Dependingvuponthe design and the intended used of such devices, the temperature ranges at which they operate may be separated into a range between 900 F. and about 1200 F. and into a range upwards of1200 up to about 1500 F. Associated parts and apparatus may be required to withstand tempera-v temperatures; theamaterialslibecomezzexnessiyel I tures of about 7 00 F. and above. In devicesoperating within the lower temperatureranige. generally much higher stresses are applied. than in devices operating above 1200 F, 'In many instances it is desired that alloys ion-use in such apparatus be capable of being hot-worked and machined, while in other'instances the alloys maybe employed in the form of castings. In any event, the alloys must have high strength.

A number of alloys have been proposed for use at high temperatures, but the utility of these alloys has been limited either because they are not hot-workable or machinable, or because they become brittle upon prolonged exposureto high temperatures. One of the characteristics of'highly alloyed ferrous materials is that as.

high temperature strength; the stability of the materials at high. temperaturestends .to decrease -50 that onprolonged exposure to high 55:

brittle.

It {is the mrin-cip provided; ferrous-.;alloys. suitable, for. use in ape iplications-lwhere temperatures above about 700 F. are-.nonnally ,z'encountered; A; further. object is thQZDI'QViSiDKI'iD'f hot-workable and machinableialloys for use at such elevated temperatures...

Another;object :isW-the .provisionof alloys capable f. withstanding; severe: vmechanical stress at The invention; by; means; of which theseob= jects are achieved .is based on the discovery that,

the :additionqofz small,- properly-proportioned quantitiesmf: tungsten at least 0116'? element; se-

lected frorn-thepgroup consistingof columb'ium;

tantalum and. titaniumaandat least one element. selected ;from. the-gr0upiconsistin ;of boron and aluminum to ironechromiummobalt alloys produces. aremarkablairicrease in the high temperature i strength. ofv suchalloys. without detrimentally affecting their high temperature.

stability.

The invention comprises alloys containing 10% to"% chromium, 10%" to"% cobalt, 0.5% to l5.%,;tungsten,. 0.5% ,to'7% in the aggregate of at least one metal selected from the group consisting of columbium, tantalum, and titanium, I and;0.01%' to 3%. in the aggregate of at least 1 one element 'selected from the group consisting of boron andaluminum, the maximum boron contentxbeing 0.7% and the minimum aluminum;

- content in the absence of boron beingv 0.5%, the

remainder ofmthev alloysbeing iron except for incidental impurities and-small quantities of elements..icustomarilyl present in steels of. good quality. The ironricontent. should always. bev

more than 5%; Noanore than 2% of titanium should, be presentJn-the. alloys. Up. to about 7.5% molybdenum may be-present in the alloys, a generallypreferred". range for molybdenum bein -0.5% to 5%. Inthe absence of mo1ybde-- num. the tungsten contentshould be at least 7.5%. If both molybdenum and tungsten-are present,- the tungsten .content pref erablyv should not exceed 10% of the alloy;

Carbon is always presentin'thealloys of the inventiombut should be less than: 1%, and if hot working; of the; alloys is desired,- the maximum carbon content should rbe. 0.35-% Nitrogen .1

" 2,513,471 N f f is importantly beneficial and is preferably present in a proportion up to 0.25%. Silicon and manganese may be present, the silicon content preferably not exceeding 1% and the manganese Similarly, the proportions of molybdenum,

tungsten, columbium, tantalum, titanium, aluminum, and boron present in the alloys affect hotworkability and weldability. A preferred upper content not exceeding 2% if hot working is de- 5 limitfor columbium and tantalum is;5%. Too sired. high a proportion of any of theseelements has A useful test for determining the suit il y a detrimental effect on hot-workability and weld- Of materials o e at high temperatures is the ability, particularly the latter property. Alloys so-called stress-rupture test. In this test several. within the composition limits defined may be samples of an alloy to be tested are maintained welded readily by any of the common welding at a given temperature. each S p e being Submethods, for example, electric arc, oxyacetylene, jected to a different measured stress. The time submergedmelt electric welding, or solid phase required to cause failure of the Samples e pressure welding-sound, strong and tough welds these conditions of temperature and stress is debein prdduced without undue embrittlement of rmin d. and the i a s r ss v s 0 weld metal or base metal, and such welds retain tained a plotted o yield a curve for the partheir toughness at elevated temperatures. Howticular material under test. From this curve can ever, if too high a proportion of any of these be determined the stress the material will Withelements is present in the alloys, welds produced Stand for a given Period of time, l 1000 hours usually sufier from loss of toughness at elevated at the particular temperature for which the temperatures curve was drawn. This test provides a convenient Likewise, the proportion of cobalt is important, method of det n g the d carrying ability and should be sufiicient to produce a stableof amaterial. It also gives some indicationof t mt a11oy I i whether or not the material becomes embrittled The presence' f t g n th alloys of t p P nged exposure at the temperature of invention within the range indicated is important, the test. A brittle material will break without nitrogen havinga beneficial effect on t high elongation, whereas ductile material will elongate temperature stability of t ll before failure. Being hot-workable, m'achinable, weldable, and Stressp u e tests conducted in the manner castable, and possessing remarkable strength at just described indicate that the alloys of the inelevated temperatures uni-.0 about 1500 F., the vention ma a great th at te p u alloys of the invention are particularly well suited as h as 1500 F. and. that even at such high to use in the fabrication (if-articles such as parts temperature the ys possess good ductility. of superchargers, gas turbines, jet propulsion apyp examples of the high temperature paratus and the like which are required to with- Strength Of chromium-cobalt Steels imparted y stand severe mechanical stress at elevated temthe addi of molybdenllrrl. tungsten, l r peratures. Their freedom from embrittlement um and boron or aluminum in various com blnaupon prolonged exposure at high temperatures tions are indicated by the data 'in the table berecommends their use e e 'dependabihty of low. In this table are reported the results of operation isessential; stress-rupture tests in which stresses of 25,000, 40 s: a s a contmuationqmpart of 30,000 and 35,000 pounds per square inch our copending application," Serial No. 599,305, P- r applied t0 east Samples of the filed June 13, 1945, now Patent No. 2,432,614 steels to be tested whilethe samples were mainissued lg 1947 tained at a temperature of 1500 F. The time in We u h urs quir for the s pl to f l und these 1. A heat resisting alloyarticle which is useful" extremely severe conditions is report d in h at elevated temperatures upwards of 700 Fiend I table. has great strength and stability when subjected Table Composition-Remainder Substantially All Fe Hours gg g g gg gggz F and Percent Percent Percent Percent Percent Percent Percent Percent 25,000 30,000 35,000

Cr 0 Mo *W O B Al O p. s. i. p. s. i. p.-.sl'i.

18.5 35 4 4 1 0. 51 Nil 0.10. 911v 195: no test 18.5 35- 4 4 1 Nil 1 0.11 113 14 no test 1s 40 a 10 1 0.5 Nil 0.10 'no test notest 3451'; 18 40 Nil 1 l5 1 0.5 Nil 0.10 no test. note'st I 443 i The data in the above table clearly illustrate the so to severe stresses at such elevated temperatures ability of the alloys of the invention to withstand large stresses at elevated-temperatures for prolonged periods of time without failure. I

In manufacturing the alloys of this invention care should be taken that the composition limits set forth be closely adhered to with regard to the intended use of the alloys since material variations in the proportions of the several ingredients detrimentally afiect the desired properties. For example, if the alloys are to be employed as castings, the carbon content may exceed"0.35% but should be less than 1%; but if hot-workability is desired, the car-bon'content should be kept at a maximum of about 0.35% and preferably should not exceed 0.2%.

for prolonged periods of time, said article being composed ofv a machinable, weldable, castable and hot-workable alloy consisting of 10% to 30% chromium; 10% to 45%, cobalt; 0% to,7.5%g l bden 0-5 t ,1. sst t un ste content being at least 7.5% when molybdenum is absent andthe tungsten content being not more than 10% when both molybdenum and tungsten are'pre's'ent; 0.5%f to 7% in the aggregate of at least one metalselectedjfrom the group consisting of colurnbium, tantalu 'nandtitanilun, the'titani um content" not exceeding"2%;"0;01% to3'% in the aggregate ofat lea'stone element selected from the group consistingoi boronand aluminum, 'Zl5' the-maximum boron content"being'0.7% andthe minimum aluminum content in the absence of boron being 0.5%; carbon in a proportion less than 0.35 nitrogen in a proportion up to 0.25 the remainder of the alloys being iron and incidental impurities, the iron content exceeding 5%.

2. A heat resisting alloy article for service at elevated temperatures upwards of 700 F. and cap-able of withstanding severe stresses for prolonged periods of time when used at such elevated temperatures, said article being composed of a hot-workable alloy consisting of 10% to 30% chromium; 10% to 45% cobalt; to 7.5% molybdenum; 0.5% to 15% tungsten, the tungsten content being at least 7.5% when molybdenum is absent and the tungsten content being not more than 10% when both molybdenum and tugnsten are present; 0.5% to 7% in the aggregate of at least one metal selected from the group consisting of columbium, tantalum and titanium, the upper limit for columbium and tantalum being and the titanium content not exceeding 2%; 0.01% to 3% in the aggregate of at least one element selected from the group consisting of boron and aluminum, the maximum boron content being 0.7 and the minimum aluminum content in the absence of boron being 0.5%; carbon in a proportion not exceeding 0.2%; nitrogen in a pro portion up to 0.25%; the remainder of the alloy being iron and incidental impurities, the iron content exceeding 5%.

3. A heat resisting alloy article for service at elevated temperatures upwards of 700 F. and capable of withstanding severe stresses for prolonged periods of time when used at such elevated temperatures said article being composed of a machinable, weldable, castable and hot-workable alloy containing to 30% chromium; 10% to 45% cobalt; 0.5% to 5% molybdenum; 0.5% to 10% tungsten; 0.5% to 7% in the aggregate of at least one metal selected from the group consisting of columbium, tantalum and titanium, the upper limit for columbium and tantalum being 5% and the titanium content not exceeding 2%; 0.01% to 3% in the aggregate of at least one element selected from the group consisting of boron and aluminum, the maximum boron content being 0.7% and the minimum aluminum content in the absence of boron being 0.5%; carbon in an effective amount not exceeding 0.2%; nitrogen in a proportion up to 0.25%; the remainder of the alloy being iron and incidental impurities, the iron content exceeding 5%.

4. A heat resisting alloy article for service at elevated temperatures as high as 1500 F. and capable of withstanding stresses upwards of 25,000 p. s. i. at such elevated temperatures for prolonged periods of time without failure, said article being composed of an alloy consisting substantially of 18% chromium; cobalt; 15% tungsten, 1% columbium; 0.5% boron; 0.10% carbon; the remainder iron and incidental impurities.

RUSSELL FRANKS. WILLIAM O. BINDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,376,062 Albrecht Apr. 26, 1921 1,729,154 Clawson 1- Sept524, 1929 1,774,862 Wissler Sept. 2, 1930 2,213,207 De Golyer Sept. 3, 1940 2,244,517 De Golyer June 3, 1941 2,245,366 Rohn June 10, 1941 2,309,372 Wissler Jan. 26, 1943 2,397,034 Mohling Mar. 19, 1940 2,398,702 Fleischmann Apr. 16, 1046 2,432,614 Franks et a1 Dec. 16, 1947 2,432,615 Franks et al. Dec. 16, 1947 2,432,618 Franks et al. Dec. 16, 1947 FOREIGN PATENTS Number Country Date 219,293 Great Britain May 7, 1925 308,549 Great Britain Mar. 28, 1929 OTHER REFERENCES Kinzel and Franks: Alloys of Iron and Chromium, published by McGraw-Hill Book Co., N. Y., vol. II, 1940, pages 87, 88, 180, 192, 194, 455.

Progress Report on NDRC, Research Project NRC-8, P. B. 39, 578, October 7, 1942, pages l-21 inclusive (particularly page 5). Declassified to open January 28, 1946. 

1. A HEAT RESISTING ALLOY ARTICLE WHICH IS USEFUL AT ELEVATED TEMPERATURES UPWARDS OF 700*F. AND HAS GREAT STRENGT5H AND STABILITY WHEN SUBJECTED TO SEVERE STRESSES AT SUCH ELEVATED TEMPERATURES FOR PROLONGED PERIOD OF TIME, SAID ARTICLE BEING COMPOSED OF A MACHINABLE, WELDABLE, CASTABLE AND HOT-WORKABLE ALLOY CONSISTING OF 10% TO 30% CHROMIUM; 10% TO 45% COBALT; 0% TO 7.5 MOLYBDENUM; 0.5% TO 15% TUNGSTEN, THE TUNGSTEN CONTENT BEING AT LEAST 7.5% WHEN MOLYBDENUM IS ABSENT AND THE TUNGSTEN CONTENT BEING NOT MORE THAN 10% WHEN BOTH MOLYBDENUM AND TUNGSTEN ARE PRESENT; 0.5% TO 7% IN THE AGGREGATE OF AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISING OF COLUMBIUM, TANTALUM, AND TITANIUM, THE TITANIUM CONTENT NOT EXCEEDING 2%; 0.1% TO 3% IN THE AGGREGATE OF AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF BORON AND ALUMINUM, THE MAXIMUM BORON CONTENT BEING 0.7% AND THE MINIMUM ALUMINUM CONTENT IN THE ABSENCE OF BORON BEING 0.5%; CARBON IN A PROPORTION LESS THAN 0.35%; NITROGEN IN A PROPORTION UP TO 0.25%; THE REMAINDER OF THE ALLOYS BEING IRON AND INCIDENTAL IMPURITIES, THE IRON CONTENT EXCEEDING 5%. 